In a polymer-electrolyte-membrane (PEM) fuel cell, a polymer membrane serves as the electrolyte between a cathode and an anode. The polymer membrane currently being used in fuel cell applications requires a certain level of humidity to facilitate conductivity of the membrane. Therefore, maintaining the proper level of humidity in the membrane, through humidity/water management, is very important for the proper functioning of the fuel cell.
During the conversion of hydrogen and oxygen (air) to electricity in the fuel cell, water is produced as a reaction by-product. The product water is removed from the fuel cell by a cathode exhaust conduit. Due to the moist operation conditions of the fuel cell, the operating parameters are chosen in such a manner that certain water saturation is reached at the cathode exhaust outlet.